'Tiny' climate changes may trigger quakes

In papers published by the Royal Society, researchers warned that melting ice, sea level rises and even increasingly heavy storms and rainfall - predicted consequences of rising temperatures - could affect the Earth's crust.

Even small changes in the environment could trigger activity such as earthquakes and tsunamis.

And some evidence suggests the consequences of climate change were already having an impact on geological activity in places such as Alaska, researchers writing in the journal the Philosophical Transactions of the Royal Society A said.

Bill McGuire, of the Aon Benfield UCL Hazard Research Centre at University College London, and the author of a review in the journal of research in the area, said warming temperatures melted ice from ice sheets and glaciers and increased the amount of water in the oceans.

As the land "rebounds" back up once the weight of the ice has been removed - which could be by as much as a kilometre in places such as Greenland and Antarctica - then if, in the worst case scenario, all the ice were to melt - it could trigger earthquakes.

A potential additional risk is from "ice-quakes" generated when the ice sheets break up, causing tsunamis which could threaten places such as New Zealand, Newfoundland in Canada and Chile.

The reduction in the ice could also stimulate volcanic eruptions, according to the research.

And the greater weight of the water in the oceans where sea level has risen as ice melts can "bend" the Earth's crust. This produces magma and causes volcanic and seismic activity in coastal or island areas - where the majority of 550 volcanoes whose eruptions have been historically documented are found.

Increased volcanic activity could cause more landslides, and have impacts well beyond the area where the volcano is situated - for example by releasing sulphur clouds into the atmosphere or by affecting air travel.

Prof McGuire said the changes could occur in the coming decades or over centuries, rather than thousands of years, depending on factors such as how quickly sea levels rose.

And he warned: "The rise you may need may be much smaller than we expect. Looking ahead at climate change, we may not need massive changes.

"One of the worries is that tiny environmental changes could have these effects."

His review said there was "mounting evidence" of seismic, volcanic and landslide activity being triggered or affected by small changes in the environment - even specific weather events such as typhoons or torrential rain.

Prof McGuire said that in Taiwan the lower air pressure generated by typhoons was enough to "unload" the crust by a small amount and trigger earthquakes.

Other impacts of rising temperatures include glacial lakes bursting out through rock dams and causing flash flooding in mountain regions such as the Himalayas, as well as rock, ice and landslides as permafrost melts.

And he said there may be "tipping points" in the geological systems, where the crust reaches a threshold that causes a step-change in the frequency of such events - but it was not clear where those thresholds might lie.

At times in the past climate change has been seen to have links with enhanced levels of potentially hazardous geological activity - for example after the end of the last ice age.

But they have not been fully considered as potential impacts of the rapid changes in the climate expected in the future and there was a great deal of uncertainty about what might happen in coming years.

Prof McGuire called for a programme of research focusing on the potential geological hazards that global warming could bring, with the leading body on global warming, the Intergovernmental Panel on Climate Change (IPCC), addressing the issue directly in its future assessments.